The present invention concerns a novel electroluminescent display and, more particularly, an electroluminescent display formed of a matrix of individual light-emitting elements in a row and column formation and adapted for excitation from a voltage supply which addresses the matrix.
Prior art electroluminescent displays are known in which the elements which make up the display layered onto a glass substrate. Typically these elements are applied to the glass substrate using vacuum deposition techniques. Such vacuum deposition techniques require expensive equipment, including an expensive vacuum chamber with high temperature deposition, for example, in the order of 600 C. or higher. Because of the high temperature required, the types of substrates which may be utilized are severely limited. Only certain glass materials are typically used because otherwise there could be significant distortion. Other problems may be created by using vacuum deposition techniques, including pinholing (where there are voids in coverage). Further, the process typically takes an extremely long time to complete the assembly of the electroluminescent display using vacuum deposition/high temperature techniques. Because of the size and expense of the vacuum deposition equipment required, only limited quantities of the displays may be produced over a selected period of time.
We have discovered a novel electroluminescent display that alleviates many of the problems concomitant with electroluminescent displays that are formed using vacuum deposition techniques. According to our invention, an electroluminescent display may be provided without using vacuum deposition techniques and without high temperature requirements.
It is an object of the present invention to provide an electroluminescent display that can be miniaturized into an appropriate form usable in a pixel type arrangement.
Another object of the present invention is to provide an electroluminescent display that can be addressed in a row and column matrix, thereby allowing for the development of appropriate selection of pixels for alphanumeric or other display purposes.
A still further object of the present invention is to provide an electroluminescent display that can be manufactured efficiently, using printed circuit and screen printing techniques, in contrast to prior art thin film sputtering techniques on high temperature glass substrates.
An additional object of the present invention is to provide an electroluminescent display that can be assembled into an extremely thin (for example, less than 0.02 inch) structure and may be flexible in both directions.
Another object of the present invention is to provide an electroluminescent display that can be formed on a large number of different substrates, including relatively thin substrates and also including substrates which cannot normally withstand high temperatures. For example, such substrates which can be used with our invention include conventional fiberglass printed circuit board material, phenolic boards, substrates formed of polyimide film, substrates formed of polycarbonate, substrates formed of fluorohalocarbon film, and others. By the nature of the aforementioned substrates and the elements used in the present invention, the entire electroluminescent display may be flexible and may be extremely thin (for example, less than 0.02 inch).
A still further object of the present invention is to provide an electroluminescent display that can be manufactured using screen printing techniques, with the elements forming the display being curable at low temperatures, such as under 150.degree. C. The substrate may include conventional fiberglass printed circuit board material, a substrate formed of phenolic material, a substrate formed of polyimide film, a substrate formed of polycarbonate, a substrate formed of fluorohalocarbon film, and others. Such substrates used in accordance with the present invention are 0.005 inch in thickness and may be as thin as 0.001 inch if desired.
An additional object of the present invention is to provide an electroluminescent display that effectively operates in the form of light-emitting capacitors, in a manner that provides significant advantages over prior art electroluminescent display techniques.
Other objects and advantages of the present invention will become apparent as the description proceeds.